The present invention relates to an apparatus and method for forming a liquid crystal alignment layer by irradiation with ion beams or atomic beams.
In a liquid crystal display (LCD), an alignment layer is provided so as to orient liquid crystal molecules. It is known that a liquid crystal alignment layer is formed by irradiating a thin film of polyimide or inorganic material with ion beams. By breaking interatomic bonds in the thin film with ion beams, an alignment film is formed.
It is needed that liquid crystal molecules are oriented uniformly all over the alignment layer. If the liquid crystal molecules are not uniformly oriented, a liquid crystal panel suffers from an unevenness of brightness and color. In order to produce an enhanced-definition liquid crystal panel, it is required to ensure much higher degree of uniformity in orientation of liquid crystal molecules than a conventional liquid crystal panel.
In order to achieve uniform orientation of liquid crystal molecules, it is necessary to ensure uniform density distribution of ion beams ejected from an ion source. Uniform density of ion beams has been so far been ensured by controlling the densities of gas and free electrons in a plasma generation chamber. However, it is apparent from various experiments that the density control is not an easy task.
As shown in FIGS. 5(a) and 5(b), while a glass substrate 24 is being moved at a constant speed, a surface of a thin film 26 is irradiated with ion beams 28 to effectively orient liquid crystal molecules. In order to orient the liquid crystal molecules of a whole surface of a thin film 26 in one direction, it is ideal that ion beams parallel to each other are applied to the thin film 26.
An ion source for generating ion beams 28 comprises a plurality of plate-like objects 11c made of electrically conductive material, as shown in FIG. 6. Such plate-like object will be hereinafter referred to as a “grid” in this specification. The grid 11c has a plurality of ion ejection holes 30 of uniform size.
However, the ion beams 28 ejected from the ion ejection holes 30 of the grid 11c are spread in various directions. In order to cut unnecessary ion beams, a mask 20 with a slit 22 is provided above the substrate 24 with the thin film 26 applied thereon. In other words, only the ion beams 28 selected for forming an alignment layer are irradiated to the thin film 26. However, if the intensity distribution of ion beams is not uniform in Y direction shown in FIG. 5(b), uniform orientation of liquid crystal molecules on the surface of the thin film 26 cannot be achieved.
Accordingly, it is an object of the present invention to provide an apparatus and method for ensuring a uniform orientation of liquid crystal molecules of an alignment layer by irradiation with ion beams.